1. Field of the Invention
The present invention relates to imaging apparatuses, and more particularly to an imaging apparatus having a function of converting a captured interlace signal to a progressive signal.
2. Related Background Art
Video cameras which capture an image signal have hitherto been known. According to the television systems, such as the NTSC system, an image signal is of 2:1 interlace type. Thus, generally, the video cameras also have a configuration which outputs an interlace type image signal of 60 fields per second.
Meanwhile, in recent years, television monitors capable of displaying a progressive type image signal instead of an interlace type signal has come into wide use. Thus, video cameras capable of outputting a progressive type image signal in addition to an interlace type image signal have also been put into practical use.
In video cameras of this type, when a captured 2:1 interlace type image signal is converted to a progressive type signal, interpolation data is generated according to a motion amount of image observed between fields to interpolate pixels to be positioned between lines by use of the interpolation data.
In this case, in order to generate interpolation data suitable for both a motion part and motionless part, for example, a motion coefficient is determined for each pixel; a signal based on intrafield interpolation and a signal based on interfield interpolation are mixed with each other with a ratio according to the motion coefficient to generate the interpolation data (refer to Japanese Patent Application Laid-Open No. S58-077373, for example).
In generating the interpolation data, when a vertical edge of an image is erroneously recognized as a motion part, a flicker of narrow edge is generated. To prevent this flicker, for example, there is also known a technique of recognizing as a vertical edge, a larger one from among the edges of the current field and previous field to thereby generate a stable edge signal (refer to Japanese Patent Application Laid-Open No. H07-131678, for example).
With the apparatuses disclosed in the above described patent documents, however, a difference of signal between fields or between frames is determined in order to obtain a motion coefficient for each pixel; therefore, when the level of luminance signal changes in a direction of the time axis, the change can be erroneously recognized as a motion.